Kaitlin Macdonald at the Big Razorback sea ice camp during a past
pupping season in this photo by field team member Erika Nunlist.

Dr. Kaitlin Macdonald successfully defended her dissertation and received her PhD from Montana State University this past Summer. Her research work on the Weddell Seal Population Project over the years has been extraordinary. And her support of our public outreach efforts has been amazing. What follows is a brief introduction by Prof. Jay Rotella, and then Kaitlin's summary of her doctoral dissertation work and findings on this long-term Weddell seal population study. Thank you, Kaitlin!

Field Blog Photo from the 2020 Weddell seal pupping season with field team leader Kaitlin Macdonald:
Our emergency cache on the north side of the Erebus Glacier Tongue. Photo by Parker Levinson.

From Prof. Jay Rotella:

Kaitlin Macdonald has been such a valuable part of the Weddell seal project. She started out as a research technician in 2014, deployed to Antarctica in 6 different years, and completed her Master’s and Ph.D. degrees on the project. She was a great field crew member and crew leader and led the team through the challenging 2020 season when reduced sea-ice in the study area and COVID-related limitations were in play. In the field, Kaitlin entered 10,038 records in the database for 4,569 different individual seals. We estimate that she has driven close to 6,000 snowmobile miles on the ice. From a scientific perspective, she’s contributed greatly with papers on diverse topics ranging from (a) energy transfer between moms and their pups to (b) the importance of super-moms to annual population growth to (c) survival differences between males and females to (d) an investigation of diverse factors that might influence which pups go on to survive to adulthood. Each of her papers have involved challenging analyses of large datasets and resulted in publications in excellent scientific journals. I am very proud and appreciative of all that she had done for the project. I’m also extremely pleased that her experience and graduate training have helped her land an excellent job that she is excited about and extremely well suited for.

Kaitlin explores a snow cave in Erebus Bay, Antarctica. Photo by Erika Nunlist.

From Dr. Kaitlin Macdonald:

This summer my tenure with the Weddell seal project concluded with my doctoral dissertation defense. My dissertation was the culmination of many years of field work, analysis and writing. I wouldn’t have been able to investigate the questions of my dissertation without the incredible research of those who have previously worked on the project as my research built upon their findings.

For my first chapter I investigated how variance in the reproduction rate of individual female seals impacts the population growth rate of the Erebus Bay Weddell seal population. I found that while female Weddell seals that reproduce more often may have many more pups over the course of their life, changing the number of this type of female in the population doesn’t change the population growth rate by an appreciable amount. This was an interesting finding but in the context of Weddell seal life histories it makes sense since so few pups survive to adulthood and that adult survival is quite important to population growth.

For my second chapter I compared the survival rates of male and female Weddell seals throughout life. Similar to many mammal species male Weddell seals have lower annual rates of survival throughout life and have shorter lifespans. Interestingly, we know female Weddell seals experience huge energetic costs during reproduction so it might be predicted that they would exhibit lower survival rates and show greater declines in annual rates of survival as adults but this prediction was contrary to our findings. Currently, much less is known about the energetic demands of reproduction for males, which include fierce combat for mating opportunities with females. It will be interesting if in future research we can identify the energetics costs of reproduction for males and compare these with those for females which may help to explain these results.

Lastly, for my third chapter I investigated what factors were important to the survival of pups during the juvenile period. I found that the most important factor to survival of pups through the juvenile period was the mass of the pup at weaning. The heaviest pups have a 28% probability of surviving and returning to our study area by six-years old, which means that even pups with more resources at weaning still face quite a low probability of surviving and returning to our population as adults.

After investigating three very interesting questions regarding seals I have switched gears and I am now working as a postdoctoral researcher with MSU and Montana Fish Wildlife and Parks. For this new position my research focuses on identifying habitat use of mountain goats in my backyard, the Bridger range. This has been a different, interesting project and brings me back full circle to where I started my career in ecology working as a technician studying mountain goats in the greater Yellowstone area.

As I reflect back on my time with the Weddell seal project I am in awe of how many wonderful people I had the opportunity to work with, the wonderful memories I made, and the sheer amount I learned on this project. The skills I acquired range from seal wrangling to data wrangling and everything in between. The memories I come away with include a beautiful picnic dinner with the crew outside our field camp huts, watching pups take a tentative first slide into the water as they learn to swim, and the pride I felt for our crew after each successful year of field work, but especially for our three-person crew during the unconventional deployment in 2020. I am incredibly grateful to have had the opportunity to work on this project!

– Dr. Kaitlin Macdonald